Spark-plug



W. B. POHLE.

SPARK PLUG.

APPLICATION FILED JULY 30, 1919.

1,391,691, PatntedSept. 27, 1921.

811a Z'Fe 733F077 2e 1145a (5W0 r22 e56 UNITED STATES PATENT OFFICE.

WALTER IB. POHLE, OF LYNN, MASSACHUSETTS, ASSIGNOR OF ONE-HALF TO ALFRED CHARLES PAGE, OF WOLLASTON, MASSACHUSETTS. I

SPARK-PLUG.

Application filed July 30, 1919.

To all whom it may concern:

Be it known that I, WALTER B. PoHLE, a citizen of the United States, and resident of L nn, in the county of Essex and State of assachusetts, have invented new and useful Improvements in Spark-Plugs, of which the following is a speclfication.

This invention relates to plugs communicating with the interior of the explosion chamber of an explosion motor, and adapted removably to close an opening in the wall of the explosion chamber.

Heretofore, as far as I am aware, spark plugs have been customarily constructed with a central terminal post carrying one of the spark terminals, and insulated from the threaded sleeve by means of which the plug is attached to the engine cylinder, by a bushing of insulating material which is of such character as to afford the proper insulation against the high potential ignition current, and to withstand the high temperature of the combustion chamber of the engine. In order to secure a gas tight joint between the sleeve and the bushing it has been necessaryto employ gaskets between the sleeve and the bushing, and screw fittings for retaining the askets in place. This construction not on y renders the spark plug more expensive to make but renders the plug difficult to disassemble for cleaning. Furthermore, such plugs must be entirely removed from the engine cylinder when it becomes necessary as in cold weather to prime the engine, unless the engine is provided with special priming. cocks or other priming equipment.

A principal\ object of my invention is to overcome the objections hereinbefore noted, to provide a plug which is simple to manu facture, easy to assemble and disassemble for cleaning, and to provide a plug which is so constructed that access may readily be had therethrough to the engine cylinder for the insertion of priming liquid without necessitating the removal of the plug. This object is attained by providing a self-seal ing joint between the supporting sleeve and insulating bushing, which automatically seals under the. explosion pressure within the engine cylinder, but which may be readily unsealed without removal of the plug sleeve from the cylinder wall for enabling the insertion of priming fluid or to reduce the compression within the engine cylinder to Specification of Letters Patent.

Patented Sept. 27, 1921,.

Serial No. 314,318

enable the engine to be more easily cranked, or unsealed after the removal of the plug fqr adequately cleaning the terminals of the I will now describe the invention in connection with one illustrative species of the genus of my invention.

In the accompanying drawings Figure 1 is an elevational View of my i mproved spark plug;

Fig. 2 is an end view of the plug showing the construction and arrangement of spark terminals;

Fig. 3 is an elevational view of my improved plug the supporting screw-threaded sleeve being shown in section to better disclose the self-sealing joint between the sleeve and the insulating terminalpost bushing;

Fig. 4 is a view similar to Fig. 3, but show,- ing the terminal post depressed within the sleeve to enable the' insertion of priming fluid;

Fig. 5 is a longitudinal axial section taken .on the line 55 of Fig. 1;

Fig. 6 is a detail view showing a modified form of spark plug; and

Fig. 7 1s a top view of the plug shown in Fi 6.

Th the drawings I have illustrated my improved spark plug as comprising a threaded sleeve 1 having a hexagonal nut portion 2 and provided with a tapered bore 3. The taper of the bore is made very gradual, the greatest diameter of the bore being at the threaded end of the sleeve. around the threaded end of the sleeve 1 and extending therefrom parallel to the axis of the sleeve are spark terminals 4. Slidable within the sleeve 1 is a terminal post 5 provided at its lower end with a collar 6 and a perforated disk 7 which serves as a spark terminal and which cooperates with the terminals 4.

The post 5 is surrounded by a tube 8 of insulating material upon which are assembled a plurality of washers 9 of suitable heat-resisting insulating material such as pressed cotton-fiber or mica. These washers are clamped together to form a compact bushing member by means of a washer 10 and a nut 11 which has threaded en agement as at 12 with the upper end 0 .the terminal post 5. The bushing is tapered from the lower end thereof toward the upper end thereof to correspond to the taper Positioned "injected of the bore of the sleeve 1 so that when the bushing is positioned within the sleeve as shown in Fig. 3, a gas-tight joint is formed between the sleeve and the bushing. A knurled thumb-nut 13 is threaded upon the upper end of the terminal post 5 by means of which an ignition cable may be connected to the terminal post. The knurled portion of this nut is made of slightly greater diameter than the diameter of the upper portion of the bore 3 of sleeve 1 so as to prevent the insulated terminal post 5 from dropping into the engine cylinder when the post has been depressed Within the sleeve as shown in Fig. 4 for the insertion of priming fluid.

In Figs. 6 and 7 I have shown the knurled thumb-nut 13 provided with a notch 14 which communicates with the circumferential channel 15 of the nut. This notch in cooperation with the channel 15 serves to conduct fluid from the spout of a suitable priming vessel as for example an oiling can, to the annular space formed between the sleeve and the insulating bushing of the terminal post when the post has been depressed to such a position that the lower face of the knurled portion of the nut 13 rests upon the upper face of the sleeve 1. nder normal operation conditions the respective parts of the plug occupy positions such as shown in Fig. 1 and the tapered insulating bushing of the terminal post 5 is forced into a gas-tight relation with the tapered bore-of the sleeve 1, by the force of the explosions within the firing chamber of the engine, which force is applied against the bottom of the bushing and against the spark terminal disk 7 The contact between the bushing and sleeve is very intimate owing to the length of the contact surface and the wedging action of the tapered bushing against the tapered wall of the bore 3.

hen it is desired to piime the engine cylinder it is only necessary to depress the terminal post with the bushing thereby separating the bushing from the sleeve thus providing an annular space therebetween through which the priming fluid ma be into the firing chamber. hen the terminal post is depressed the compression' within the firing chamber is released and the engine may thenbe more easily cranked. Upon the first explosion, however, the plug automatically seals the firing chamber and thereafter functions in that usual manner.

The construction hereinbefore described renders the spark plug readily disassembled for cleaning. To clean the plug the sleeve 1 is first unscrewed from the cylinder. The

i 7 for cooperation tight oint knurled nut 13 is then removed and the entire terminal post removed from the sleeve. Access may then be had to the spark terminals 4 on the sleeve and to the disk terminal 7 onthe post, so that they may be thoroughly cleaned. This is not possible with the ordinary spark plug.

While I have illustrated a disk terminal with the spark terminals 4, it is apparent that the terminal 7 might be of any other suitable shape.

From the foregoing description it is apparent that I have provided an improved spark-plug which requires no gaskets, which is self-sealing, which is easily disassembled to expose the entire surface of the spark terminals for proper cleaning, which is so constructed that priming fluid may be injected into the firing chamber through the spark-plug sleeve without removing the plug, and which is simple in construction and relatively inexpensive to manufacture.

I claim:

1. In a spark plug the combination of a sleeve having a tapered bore, a spark terminal thereon, a terminal post slidable within said sleeve and insulated therefrom by an insulating bushing tapered to form a gastight joint with said sleeve in the raised position of said post within said sleeve, a spark terminal carried by said post, and a binding post nut having screw-threaded engagement with the upper end of said post, said nut having an external diameter greater than the diameter of the bore of said sleeve, whereby when said post is depressed within said sleeve, said post is prevented from passing entirely through said sleeve.

2. In a spark plug the combination of a sleeve having a tapered bore, a spark terminal thereon, a terminal post slidable within said sleeve insulating bushing tapered to form a gaswith said sleeve, a spark terminal carried by said post and a binding post nut having a screw threaded engagement with the upper end of said post, said nut having an external diameter greater than the diameter of the bore of said sleeve and provided with a notch in the circumferential surface thereof which when said post is depressed within said sleeve communicates with the annular space between the surfaces of said bore and post whereby priming fluid may be injected. 5

Signed by me at Boston, Massachusetts, this twenty-first day of July, 1919.

WALTER B. POI-ILE.

and insulated therefrom by an 

